1. Field of the Disclosure
The present invention relates to a thin film transistor substrate and a method for fabricating the same, and more particularly to a thin film transistor substrate and a method for fabricating the same which can reduce a number of fabrication steps.
2. Discussion of the Related Art
A liquid crystal display device controls light transmissivity of liquid crystals having dielectric anisotropy by using an electric field to display a picture. The liquid crystal display device is provided with a liquid crystal panel having a thin film transistor substrate and a color filter substrate bonded together to face each other, a backlight unit for directing a light to the liquid crystal panel, and a driving circuit for driving the liquid crystal panel.
The thin film transistor substrate has gate lines and data lines formed to cross each other with a gate insulating film disposed therebetween on a lower substrate, a thin film transistor (TFT) formed at every crossed portion thereof, a pixel electrode in contact with a drain electrode of the thin film transistor through a contact hole, and a lower alignment film coated thereon.
The color filter substrate has a color filter for producing a color, a black matrix for preventing a light from leaking, a common electrode for forming a vertical electric field to the pixel electrode, and an upper alignment film coated thereon for alignment of the liquid crystals.
Thus, the liquid crystal panel can be fabricated in a TN (Twisted-Nematic) mode in which an electrode is provided to each of the substrates, the liquid crystals are arranged such that a director thereof is twisted at 90° and a voltage is applied to the electrodes to drive the director, and operated by using an IPS (In-Plane Switching) mode in which the director of the liquid crystals are controlled with a horizontal electric field formed by two electrodes on one substrate, or an FFS (Fringe Field Switching) mode in which liquid crystal molecules are made to move by a fringe field formed between two electrodes of a transparent conductive material with a small gap therebetween.
The thin film transistor substrate of a liquid crystal panel using the FFS mode is fabricated by a method including steps of forming a gate electrode by using a first mask, forming a semiconductor pattern by using a second mask, forming source/drain electrodes by using a third mask, forming first protective film having pixel contact holes and pad region contact holes by using a fourth mask, forming a pixel electrode by using a fifth mask, forming second protective film and pixel contact holes and pad region contact holes in the second protective film by using a sixth mask, and forming a common electrode on the second protective film by using a seventh mask. As such, the method for fabricating the FFS mode thin film transistor substrate requires at least seven masking steps, and thus a process cost and time is great.